Gay black men have a higher risk of HIV infection than the general gay population, a phenomenon unexplained by their number of sexual partners, injection drug use or age, aidsmap reports. Researchers from the University of California at San Francisco and the San Francisco Department of Health analyzed data from four surveys conducted with gay men of varying ethnicities and races between 1992 and 2003 and presented their findings at the 20th Conference on Retroviruses and Opportunistic Infections (CROI) in Atlanta.

Between the four studies—Jumpstart (conducted before the modern era of antiretrovirals, or ARVs), HIVNEXT VPS, EXPLORE and VAX004—the investigators analyzed data on 10,760 gay men who between them paid 42,395 semi-annual trial visits; 584 of them became infected during the studies. The researchers only admitted data into their analysis from participants who reported at least one incident of unprotected insertive or receptive anal intercourse, protected receptive intercourse, unprotected intercourse with a partner of unknown HIV status or unprotected sex with more than one partner who purported to be HIV negative.

Overall, a man’s risk of contracting HIV for each sexual contact with a male partner known to be HIV positive was one in 137 contacts for unprotected receptive anal sex (0.73 percent), one in 455 contacts for unprotected insertive sex (0.22 percent) and one in 1,250 contacts for protected receptive sex (0.08 percent). These calculations were drawn from the three post-ARV era studies.

Between the four studies, the average risk for contracting HIV from unprotected receptive sex with partners of unknown HIV status was one for every 204 sexual contacts.

Before adjusting for other factors, the investigators found that gay men younger than 25 had a 31 percent higher per-contact risk of becoming infected, while young black men’s risk was 78 percent higher. However, young black men actually had fewer unprotected sex contacts: In a six-month period, young black men had an average of three receptive and five insertive sex acts without a condom, compared with a respective 11 and 12 among young white men.

Adjusting the analysis for age, the researchers found that black gay men have a 22 percent higher per-contact risk of contracting HIV than the rest of the gay population.

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